1. Field of the Invention
The present invention relates to method and means for splicing a new roll of web material into an expiring roll of web material while the web is moving.
2. Prior Art
In order that it not be necessary to shut down machinery used for processing web material such as, for example, paper coating machinery, it is advantageous to be able to splice a new roll of web material onto the moving web of the expiring roll being processed. With slow moving webs, this can be accomplished by a skilled operator manually without the need for sophisticated mechanical and electronic devices for monitoring movement of the web, and further, it can be accomplished while leaving a relatively long tail on the expiring web since the web is moving so slowly that after the splice is made, the operator can then sever the trailing edge from the moving web providing only a short overlap so as not to interfere with the subsequent processing equipment. However, as the speed of processing increases, it becomes impossible for the operator to splice the new roll of web material manually into the moving web, and either mechanical means must be used to accomplish this, or the machinery must be stopped or substantially slowed down while the splice is manually accomplished.
Several devices have been developed which accomplished splicing of the moving web. For example, such devices are disclosed in U.S. Pat. Nos. 3,276,710 and 3,253,795. The first of these utilizes a free knife blade which is mounted directly to the leading edge of the new web and its splicing strip, and which cuts through the old web after the splicing strip has been adhered to the old web with the blade then being discarded from the moving web. This forms a fairly accurate butt splice when used with certain web materials, but might not completely or smoothly sever some web materials such as those which would be highly elastic like thin plastic films, and thus has a limited use for high elasticity materials.
The other of these devices produces a lap joint between the trailing edge of the severed old web and the leading edge of the new web, which can cause processing problems in the coating or other processing equipment downstream from the unwinder/splicing equipment. Further, although this type of splicing mechanism is sensitive to roll diameter, line speed changes and consistency of knife actuation time, since no control over knife movement is maintained during knife actuation tail length accuracy is less than desired. When the diameter of the new roll is greater or less than the nominal diameter used for calculating the time interval for cutting, and when the web speed is faster or slower than the nominal web speed, the splice is not accurate and results in exposed glued area or loose tail, either of which conditions can result in damage to the downstream processing equipment or defects in the ultimate product.